The rehabilitation of water, gas, and drainage networks has for many years involved “trenchless” technologies, i.e. technologies that consist in inserting a tubular liner inside an existing pipe, the liner generally being made of a flexible material such as a thermoplastic material, a thermosetting material, or a thermosetting composite material, said liners either being inserted after being folded in half along a longitudinal generator line so as to provide them with a cross-section in the form of a kidney bean, and subsequently being returned to the round merely by applying internal pressure, or else they are pulled through by being put under traction so that the diameter of the liner is reduced to a value that is smaller than the inside diameter of said pipe. Thereafter, once the liner has been pulled through, tension in the liner is released and said liner then returns to its initial diameter, thereby naturally pressing against the inside face of said pipe. That insertion technique is known as “swagelining”, and it is commonly used for rehabilitating water or gas pipes over unit lengths that may be as much as 500 m, or even as much as one kilometer in a straight line.
That technology is also used when transporting corrosive fluids under high pressure, thus making it possible to use a pipe for withstanding pressure that is made of steel or carbon in conventional manner, and that is therefore inexpensive, and easy to work by being welded, while resistance to corrosion is ensured by the inner liner. Unit lengths can thus be achieved that can be several hundreds of meters long and that then need to be connected together, while ensuring continuity in protection against corrosion. Three types of connection are in widespread use: connections via flanges, screw connections, and welded connections. When making a connection by means of flanges, it suffices to fold the liner back over the face of the flange, with the clamping of the flanges then pinching the liners face to face and thus providing continuity in the anti-corrosion function. With screw joints, continuity can be provided, for example, by a ring fitted with gaskets that provide sealing with each of the upstream and downstream liners. With welded connections, it is appropriate to interrupt the liner at a significant distance from the end of the pipe, e.g. 100 millimeters (mm) to 200 mm, so that the heating of the steel wall during welding does not damage the liner. The problem which then arises is how to provide protection against corrosion for the non-lined zone extending between the end of the liner in pipe N and the end of the liner in the following pipe N+1.
Patent GB-2 218 488 describes a “swagelining” method consisting in stretching a circular pipe of flexible material, referred to below as a “liner”, so as to reduce its diameter in order to enable it to be inserted in a pipe by being pulled, the rest diameter of said liner being greater than the inside diameter of said pipe. Another way of inserting such a liner is to deform it by folding it so as to obtain a cross-section that is “kidney” shaped, and that then fits within a circle of much smaller diameter, thereby enabling insertion to be performed by simple pulling along the inside of the steel pipe. After being pulled through, the considerably-projecting ends return naturally to a substantially circular shape and it is simple to fit a plug thereto. By pressurizing the liner with compressed air, the liner is returned to its circular shape and said liner thus presses firmly against the inside wall of the steel pipe.
Patent GB-2 298 256 describes a method of welding together two pipe elements or portions that are lined over their main extent, the non-lined zone being covered in an alloy that withstands corrosion, said alloy preferably being Inconel that is applied by an electric arc type process referred to as “cladding”. The parts are then re-machined so as to present grooved shapes that enable said liner to be anchored by crimping an internal ferrule, it likewise being made of a material that withstands corrosion, and preferably of Inconel. Preparing the ends of pipe elements represents a unit cost that is very high but that is not particularly significant in the overall cost providing the pipe elements used are of long unit length, e.g. several hundreds of meters. However, that cost becomes unacceptable when the unit length of each pipe element is 24 m or 48 m. In addition, the welding of the connection must be performed over the entire thickness of the pipe using the same noble metal, in general Inconel, thereby considerably complicating the work and leading to a cost that is very high, since the unit rate at which metal is deposited is much smaller and the process is more difficult to control than conventional welding on ordinary steel. Finally, it is very difficult to perform quality control on the welding, and for certain types of anti-corrosion material, it is practically impossible to perform such welding in a manner that is reliable and repeatable, in limited time.
Patent GB-2 391 597 describes a method of assembling two lined pipes by inserting around each of said liners a tubular junction sleeve that is received in a setback in the thickness at the end of the steel wall of each of the two pipes elements to be assembled together. Said junction sleeve is then secured to said liners by means of internal ferrules that are expansibly crimped using a tool inside the pipe, said tool being operated from the nearest free end of the pipe. In that patent, each of the pipe elements is bored so as to create a housing for the tubular junction sleeve, which serves as a backing for expansively crimping the internal ferrules that secure the liners to said tubular junction sleeve. The tubular junction sleeve, which is made of an alloy that withstands corrosion, is in direct contact with the steel pipe, in particular in the welding zone. This runs the risk of damage during welding if welding is not performed using the same alloy, and of corrosion in the event of water infiltrating between the liner and the outer steel pipe. In addition, the re-bored zone of each steel outer pipe presents a connection zone of thickness that is smaller than the thickness of the main portion of the pipe, thereby creating a zone of weakness.
Patent WO-2004/015321 describes a tubular junction sleeve between non-lined ends of two pipe elements for assembling together. That tubular sleeve is made of a material that withstands corrosion. On its outside surface it presents machined grooved shapes of outside diameter smaller than the inside diameter of the liner, said ferrule being expansibly crimped using a tool inside the pipe, said tool being operated from the nearest free end of the pipe. In that patent, the tubular junction sleeve is slidable in the internal bore of the liner and presents outside grooves, and the assembly needs to be expansibly crimped using a crimping tool while assembling together the ends of the two pipe elements for assembly on board a J-lay tower.
In GB-2 391 597 and WO-2004/015321, a tool for crimping by expanding the tubular junction sleeve or other connection elements needs to be positioned and operated from the free end of the pipe, i.e. from a distance of 24 m to 48 m, when laying such pipes at sea from a J-lay tower, which can present considerable technical difficulty from an operational point of view and from a quality control point of view.
Patent WO-2004/011840 describes assembling two pipe elements by means of a tubular junction sleeve inserted in the non-lined ends of the steel walls of two pipe elements for assembly. Said tubular junction sleeve is made of a material that withstands corrosion and it is fitted with sealing O-rings that provide sealing with the ends of the liners of the two pipe elements for assembly. Each of the liners is locked in position by an additional ferrule at its end, which ferrule is likewise made of a material that withstands corrosion. Said additional ferrule is expansibly crimped against the ends of said liner. At each of its ends, said tubular junction sleeve includes a portion of its outside surface that comes directly into contact with the steel wall at the non-lined ends of the pipe elements for assembly. That represents a major risk of corrosion when using a tubular sleeve of a corrosion-resistant alloy of the Inconel type and when in the presence of water at the interfaces between the tubular sleeve, the liners, and the steel walls of the pipe elements.
Furthermore, that patent actually describes a method of assembling lined pipes that are intended more particularly to convey multiphase oil, i.e. oil that can contain both gas and water, and that thus requires said liner to be “ventilated” so as to ensure that when the pressure inside the pipe is reduced, any gas that has migrated through the thermoplastic material of said liner does not cause said liner to collapse onto itself. For that purpose, the liner has microchannels enabling pressure to be balanced between the chamber extending between said liner and the outer pipe of steel, and the inside of the pipe. The tubular junction sleeve has holes for allowing pressure to balance between the chamber that exists between said connection part and the outer steel pipe, and the inside of the pipe. In addition, gas is conveyed between the left portion of pipe N-1 and the right portion of pipe N.
That type of structure for lining and assembling two pipe elements for assembly, as described in WO-2004/011840, with permanent perforations through the tubular junction sleeve, which may in part come directly into contact with the steel wall of the pipe, is thus not suitable for making water injection pipes, and in particular pipes for injecting sea water, particularly if the sea water has not been passivated.